The present invention relates to a rotatable flexible shaft transmitting torque with reduced noise and vibration.
Such shafts normally have ends of square cross-section which are adapted to engage square recesses in mating torque transmitting and receiving members. When such a shaft is rotated, noise is generated due to movement of the shaft ends within the mating recesses. It is not possible to provide an exact fit between the shaft ends and the recesses, since manufacturing tolerances must be maintained to insure the ends can be inserted into the recesses when the associated devices, such as motor vehicle seats, are assembled.
Prior art efforts to reduce such noise and vibration include applying flocked yarn or flock fibers, grease, or heat shrink tubing such as polytetrafluoroethylene to the lateral surfaces of the shaft ends. See, for example, U.S. Pat. No. 7,717,795 to Mellor.
Such prior art constructions have various disadvantages such as significant manufacturing expense, fabrication difficulty, limited durability, limited useful life, and/or a performance level less than that desired.
Patent Application Publication No. US 2008/0220883 of Yuen shows a noise and vibration reducing construction wherein felt or a material having similar mechanical characteristics is wrapped around a major part of the shaft to reduce noise and vibration due to contact with the surrounding casing. U.S. Pat. No. 5,558,578 to Uryu et al. discloses compressed felt coaxial sheaths which surround spaced portions of the shaft. However, further reduction of noise and vibration is generally desired.
Patent Application Publication No. US 2010/0252359 of Yuen shows a noise reducing construction wherein the shaft ends have raised portions of compressible material such as flocked yarn covered with plastic tubing. This construction also fails to provide the desired level of durability, useful life, and noise and vibration reduction.
Accordingly, an object of the present invention is to provide an improved reduced noise and vibration flexible shaft which can readily be manufactured at reasonable cost and which exhibits improved durability and useful life.